Zinc alloy



United States Patent Ofiiice 3,006,758 Patented Oct. 31, 1961 3,006,758 ZINC ALLOY Raymond E. Giuliani, Park Forest, and John D. Scudder, Chicago, 111., assignors to Hydrometals, Inc., Chicago, Ill., a corporation of Illinois No Drawing. Filed Jan. 5, 1960, Ser. No. 514 6 Claims. (Cl. 75178) The present invention relates to zinc alloys and more particularly to improved zinc base alloys containing copper, titanium, chromium and manganese, which alloys find particular but not exclusive use in the production of rolled strip.

United States Patent No. 2,317,179, issued April 20, 1943, to John R. Daesen describes zinc base alloys containing copper and at least one relatively high melting point metal selected from the group consisting of beryllium, zirconium, titanium, vanadium, chromium, columbium, molybdenum, tantalum, tungsten and uranium. The patentee found that, when 2% or more copper was incorporated into the zinc, from about 0.02 to about 0.50% of the relatively high melting point metals could also be added to produce alloys having high creep resistance. The patentee pointed out that when less than 2% copper was employed, for example 1% or less, it was impossible to disseminate evenly more than about 0.05% of the high melting point metals in the alloys, and that when larger amounts of the high melting metals were employed no improvements in physical properties were found. The patentee further said that alloys containing 1% or less of copper do not have the superior resistance to cold flow characterized by zinc alloys with 2% or more of copper together with the high melting metals.

United States Patent No. 2,472,402, issued June 7, 1949, to Boyle describes zinc base alloys containing copper and titanium. The patentee Boyle found that zinccopper-titanium alloys containing less than 2% copper can be made by conventional zinc alloying practice to contain as much as 0.5% or more of titanium thoroughly disseminated therein in conventional alloy fashion as distinguished from the non uniform dissemination reported by Daesen. The patentee Boyle also found that such alloys containing about 0.5 to 0.75% copper and about 0.12 to 0.25% titanium dispersed in zinc possessed excellent drawing characteristics and high resiliency in addition to high creep resistance, and the patentee further pointed out that the alloys are characterized by a creep resistance markedly superior to the alloys containing 2% or more of copper as disclosed in the patent to Daesen. He said that although 0.5% copper appeared to be the minimum for the effective properties, as little as 0.4% copper could be used together with as little as 0.10% up to 'bout 0.5% titanium.

While the alloys described by the patentees Daesen and Boyle in their respective patents do indeed have the properties ascribed to them, substantial difiiculties have been encountered in producing rolled strip stock from cast slabs of such alloys and in using and fabricating the alloy metals into useful products. The alloys described have been found to be diflicult to roll to produce coiled strip which has a clean, bright surface and a clean, untorn or unbroken edge. It has also been found to be extremely diflicult to fabricate sheet metal articles from such alloys because of the alloys lack of dynamic ductility and good cold bend characteristics.

It is accordingly the primary object of the present invention to produce an improved zinc base alloy which can be readily rolled into strip stock and which can be easily formed and shaped during fabrication of metal products therefrom. More specifically, it is an important object of the present invention to produce an improved zinc base alloy which can be cast into slabs and the slabs rolled to form coiled strips which exhibit substantially uniform crystal structure throughout, which do not split or break at the edges during rolling, and which are characterized by a clean, bright surface.

A more detailed object of the present invention is to provide an improved zinc base alloy of the above character which when cast and rolled into coiled strips exhibits a clean, bright surface and especially a surface which is not marred by dark streaks or a generally dark dull non-metallic appearance, and thereby to avoid the necessity of subsequently polishing the metal strip.

Another object of the present invention is to provide an improved zinc base alloy of the foregoing character which, after casting into slabs, can be readily hot rolled with a minimum of edge cracking, breaking, and deformation, and thereby substantially increase the amount of usable strip metal produced so that an efiicient and economical production of the alloy in strip metal form is afforded.

A further object of the present invention is to provide an improved zinc base alloy of the foregoing character which, after forming into sheet or strip, can be readily bent and shaped for use in the formation of sheet metal products and which can be radically bent in a complete reverse cold bend without cracking or weakening and which can be severely formed and deep drawn Without stage annealing thereby making the alloy extremely useful for metal fabrication industries such as construction work, sheet metal work, automobile parts, and industrial sheet fabrication in general.

Still a further object of the invention is to produce an improved zinc alloy which possesses the foregoing characteristics and which at the same time exhibits high tensile strengths and which is characterized by a high creep resistance such that structural articles made of the alloy retain their shape under static loads conventional to the use for which the articles are intended.

In accordance with our invention, we have produced zinc base alloys containing as little as between 0.15 and 0.35% copper, along with as much as 0.15% titanium, 0.05% chromium, and 0.05% manganese, with the remainder zinc, which alloys can, in fact, be made with the high melting point alloy metals uniformly disseminated therein. And, most important, such alloys exhibit substantially improved dynamic ductility and cold bending characteristics as well as substantially improved rolling and hot working characteristics. The latter properties are especially important when sheet or strips of the alloy are to be fabricated into sheet metal articles and are of major concern to those in the metal Working arts.

We have found that zinc base alloys produced in accordance with the present invention have substantially improved mechanical working properties among which are the properties of dynamic ductility and cold bend. With respect to the latter, our alloy can be given a cold bend completely back on itself to produce a two sheet thickness (referred to as a 2T or 2 bend) without cracking. Alloys produced in accordance with the present invention also exhibit smooth, clean, bright surfaces after rolling with a noticeable absence of dark streaks and any generally dull finish. The edges of the rolled strip are clean, necessitating a minimum of trimming so that a maximum amount of usable metal strip is produced, oftentimes avoiding entirely any requirement for severe trimming.

The homogenous zinc base alloys of the present invention comprise from 0.15 to 0.35% copper, from about 0.08 to 0.15% titanium, from about 0.001 to 0.05% chromium, from 0.0 to about 0.05 manganese and the balance zinc. The recited ranges of copper, titanium, chromium and manganese in the alloys of the invention represent the compositions which have been found to be effective to produce the above objects.

The mechanical properties of the alloys embodying the invention are illustrated as examples in Table 1. Mechanical properties are given in this table for a number of different alloy compositions, each falling within the to the direction of rolling and against grain is perpendicular to the direction of rolling; TS. is the tensile strength in pounds per sq. inch (p.s.i.); and TE. is tensile elongation, measured in percent in 2 inches.

Table I High Grade Zinc (.009% '1.S. (at 250 Lead) Plus B mils/m n), T E. 1n 2 p.s.1. No. Treatment 'T" F. G in H(RT) D.D. in

X1000 Cu, Ti, Mn, Or, with against with against with against Percent Percent Percent Percent grain grain A--- 0.255 0. 11 0.003 as rolled.-. 360 0.020 63 330 2T 2T 29,300 41.4 B- 0.25 0.13 0. 004 do 350 0.027 62 325 2T 2T 27, 600 34.3 C 0.27 0.12 0. 004 do 350 0.032 60 300 2T 2T 29, 800 29. 7 D-l 0.255 0. 08 0.004 0.001 do 0.020 66 335 3T 2T 27,800 38,600 25 18.7 D2 0. 255 0. 08 0.004 0. 001 45 min .Eat; 0.020 65 340 2T 2T 26, 700 35, 800 25 15. 6

483 13-3--. 0. 255 0. 08 0.004 0. 001 3 hrs aFt 0.020 64 340 2T 2T 26, 500 35, 100 25 14 483 0.25 0.12 none 0.004 as rolled 325+ 0.020 61 2T 2T 25,100 35,100 34 foregoing alloy range. The rolling treatment to which the slabs of these alloys were subjected resulted in a finishing temperature of approximately 350 to 360 F. The alloys were produced by melting high grade zinc in an induction furnace and adding amounts of the alloying materials in the usual manner. The molten zinc alloy was cast into slabs which measured approximately 10" by 40" by 80". The slabs were heated in an oven kept at 450 F. overnight and were withdrawn when they had a temperature of 420 F.

While the slabs were 10" thick when cast, they were milled or scalped, before rolling to a thickness of about 9", depending on the depth of shrinkage cracks in the cast slab. The slabs were rolled by passing them broadside between vertical rolls in four dead (i.e., no or slight reduction in thickness) passes 44" wide for the purpose of squaring the edges along the 80" dimension. During this edge rolling the thickness of the slab was further reduced slightly to about 7.36". The slabs were then sent through the rolls with the 44" dimension going into the bite of the rolls and the pressure was set to achieve the following reductions in thickness in each successive pass: 1.9, 1.5", 1.2, 0.9", 0.7", 0.5", 0.3", and 0.18. In other words, in the first pass the thickness was reduced by 1.9" or from 7.36" to 5.46". The next pass brought the thickness down 1.5 more to 8.96". Subsequent reductions brought the slab to 0.180", the final thickness off the slab mill. The passes were carried out at 450 ft. per min., maximum speed, and the finishing temperature of the rolled slabs was approximately 550 F. at the maximum.

Following the slab rolling, the strips were finish rolled after reheating to 450 F. After each pass the coil was returned to the oven and reheated to 400 F. minimum and 450 F. maximum, so that rolling was carried out above 300 F. with a preferred minimum of about 325 F. The following pass schedule was followed:

Min. 400 F. entry, .180"/ .090" Exit over 325 F. Min. 400 F. entry, .090"/.045" Exit over 325 F. Min. 400 F. entry, .045"/.027" Exit over 325 F.

In the table the alloy composition, including amounts of copper, titanium, manganese and chromium is given first, followed by the physical properties measured. In the columns of the table, T is temperature in degrees Fahrenheit; G is the gauge thickness in inches; H is the Rockwell hardness on the 1ST scale; DD. is the dynamic ductility with the units given in inches times 1000; B is the cold bend value represented by the diameter of uncracked 180 bends and multiples of gauge (sheet thickness), and thus the lower values indicate better bending properties with a value of 2 being the maximum or best possible bend; with grain is parallel In the alloy of this invention the zinc base is preferably high grade or special high grade zinc. Zinc analyzing at least 99.9% pure is preferred, and satisfactory alloys are obtained from zinc of the grade used in the production of commercial rolled zinc, for example, zinc metal containing as a maximum, .07% lead, .02% iron and .07% cadmium. It is preferred to use high grade zinc having no more than 0.002% iron, and lead and cadmium under 0.005%.

Alloys produced in accordance with the present invention do not tend to darken excessively upon exposure to the atmosphere or to various combinations of chemicals and lubricants during rolling. Further, an alloy of the composition advocated is capable of withstanding working temperatures as high as 500 F. for extended periods of time without danger of producing grain structure substantially coarser than originally existed and without adversely affecting ductility. The alloy is thus highly amenable to extrusion processes for the production of extruded shapes and to cold working and fabrication.

We claim -as our invention:

1. A high grade zinc base alloy characterized by a high dynamic ductility, ease of hot rolling and low cold bend value, containing from about 0.08 to about 0.15% titanium, from about 0.15 to about 0.35% copper, from about 0.001 to about 0.05% chromium, up to about 0.05% manganese, and the balance zinc.

2. A high grade zinc base alloy comprising from about 0.08 to about 0.15% titanium, from about 0.15 to about 0.35% copper, from about 0.001 to about 0.05% chromium, up to about 0.05 manganese, and the balance zinc, said alloy having a dynamic ductility greater than 300 and a cold bend value of 2.

3. A high grade zinc base alloy rolled strip product comprising from about 0.08 to about 0.15% titanium, from about 0.15 to about 0.35% copper, from about 0.001 to about 0.05% chromium, up to about 0.05% manganese, and the balance zinc, said alloy having a dynamic ductility greater than 300 in thicknesses of 0.18" and greater and a cold bend value of 2, and having been subjected to a finishing treatment consisting of hot rolling at a temperature within the range of about 300 F. to about 450 F.

4. A high grade zinc base alloy comprising about 0.25% copper, about 0.11 to about 0.13% titanium, about 0.004% chromium, and the balance zinc, said alloy having a dynamic ductility greater than 300 and a cold bend value of 2.

5. A high grade zinc base alloy comprising about 0.25% copper, about 0.11 to about 0.13% titanium, about 0.004% chromium, about 0.004% manganese and the 119? Zjm}, Sa d alloy having a dynamic ductility greater than 300 in thicknesses of 0.18" or more and a cold bend value of 2.

6. A zinc base alloy ro lled strip product comprising about 0.25% copper, from about 0.11 to about 0.13% titanium, about 0.004% chromium, and the balance zinc, said alloy having a dynamic ductility greater than 300 and a cold bend value of 2, and having been subjected to a finishing treatment consisting of hot rolling at a temperature Within the range of about 300 F. to about References Cited in the file of this patent UNITED STATES PATENTS 

1. A HIGH GRADE ZINC BASE ALLOY CHARACTERIZED BY A HIGH DYNAMIC DUCTILITY, EASE OF HOT ROLLING AND LOW COLD BEND VALUE, CONTAINING FROM ABOUT 0.08 TO ABOUT 0.15% TITANIUM, FROM ABOUT 0.15 TO ABOUT 0.35% COPPER, FROM ABOUT 0.001 TO ABOUT 0.05% CHROMIUM, UP TO ABOUT 0.05% MANGANESE, AND THE BALANCE ZINC. 